Photographic sound track



Oct. 14, 1941. LE ROY M. DEARING 2,258,976 PHOTOGRAPHIC SOUND TRACK Filed May 3, 1940 PR/h T PRINT JOU/YO PICTURE ma"; l8 EXPOSEO AND %/Z OEQVELOPED MEG/em.

P/CTUREAREA OF TOP LAYER 511 0550 A/vo DEVELOPED YELLOM I i I h 22 MIDDLE LAYER FOGGED 20 a 2 AND DEVELOPED MAGENTA AND J/L VER REMOVED.

A may M. [PEAR/Ne IN VEN TOR A TTOR Patented Oct. 14, 1941 PHOTOGRAPHIC SOUNDTRACK Le Roy M. Dearing, Rochester, N. Y., assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application May 3, 1940, Serial No. 333,203

4 Claims.

This invention relates to sound tracks in photographic film and particularly to a method for producing a sound track in photographic color film.

The production of a dye. sound track in reversal color processes is usually carried out in one of two ways- The sound track may be finished in the same manner as the'picture area in which case it will be made up of the same dyes as are present in the picture. A second way is to develop the sound track image by special printing'methods or by other physical means after reversal in such a way as to use only one dye for the sound image. In this case the dye chosen is usually the one which has the best infra-red absorption in order that the sound reproduction may have the bestquality. These methods have the disadvantage that dyes available for color pictures are not good infra red absorbers and give a contrast and maximum density to infra red light that is too low for satisfactory sound quality. In general, dye sound tracks give weak volume as well as poor quality sound on reproduction.

One method of overcoming these objections is to make the sound track of metal or a metallic salt. For example, silver sulfide has been used in the formation of sound images as described in Capstaff U. S.'Patent 1,973,463, September 11, 1934, and Mannes and Godowsky U. S. Patent 2,143,787, January 10, 1939. By these methods a sound track is obtained which has satisfactory contrast and whose maximum density transmits little infra-red. The sulfide sound track, however, doesnot have a clean highlight and this factor has prevented its'general use due to the poor quality sound obtained.

It is, therefore, an object of the present invention to'provide a novel photographic sound image. A further object is to provide a novel method for producing a sound track in photographic color film. A still further object is to provide a method for improving the high-light quality of a photographic sound track. Other objects will appear from the following description of my invention.

These objects are accomplished by forming the sound track of silver sulfide and silver iodide,

As stated above, I secure beneficial results in the formation of a photographic sound track by using a bath which both sulfides and iodizes the sound track. Any sulfur compound which produces silver sulfide upon reaction with silver halide may be used, together with an alkali metal iodide, such as potassium or sodium iodide.

The ratio of iodide to sulfide in the bath may be varied over a wide range of concentrations. With, some reversal films that have a high highlight density an entirely satisfactory bath may be obtained from the use of iodide alone. If greater density than that obtainable with iodide alone is desired, sodium sulfide or thiourea may be added to the solution. In this solution, which contains both iodide-forming and sulfide-forming compounds, the presence of the iodide pre-' vents excessive highlight stain while the sulfide builds up the contrast and maximum density to a satisfactory level. The gamma that can be obtained corresponds to that required for good quality sound, being in the neighborhood of a gamma of one.

In the treatment of the silver bromide or silver chloride sound image with the sulfiding and iodizing bath, the sulfide and iodide react in competition with each other. The sulfide reacts immediately and the upper part of the sound track image is usually composed largely of sulfide. The iodide penetrates through to the bottom in a slower reaction and most of the image grains in the lower part of the emulsion layer are silver iodide.

Although my invention may be used for the such as that described in Mannes, Godowsky and thereby eliminating the objectionable features of Wilder U. S. Patent application Serial No, 185,700, filed January 19, 1938. In the process described in that application a three layer film having differently sensitized emulsion layers is exposed to a subject and developed to a negative. After negative development the bottom layer of the film is exposed through the support and developed in a color forming developer. The middle layer is then exposed through the support and developed in a second color forming developer and the top layer is finally exposed from the emulsion side and developed in a .third color forming'developer after which all silver images are removed.

In my process the sound track formation may ment or after any of the three stages of color development. In a film of the type described in Mannes, Godowsky and Wilder application Serial of the middle layer.

My invention will now be described by particular reference to the accompanying drawing. As shown therein, a photographic film comprising a support I of any suitable material such as cellulose nitrate, cellulose acetate, synthetic resin or paper is coated withsuccessive emulsion layers ll, I2 and I3 sensitive respectively to the red,

green and blueregions of the spectrum. Tlus film will ordinarily contain additional filter and subbing layers not shown, especially a yellow filter layer between the emulsion layers l2 and [3 or incorporated in emulsion layer l3.

The first step in my preferred method is to print the sound and picture images in all three layers of the film. This may be done by simultaneous or successive printing steps. The film is then developed in an ordinary black and white developer such as that disclosed in application Serial No. 185,700 to form the negative metallic silver images ll, and IS in layers ll, [2 and I3, respectively, and a negative sound image ll in layers ll, [2 and I3.

The bottom layer of the film, which is red sensitive, is then exposed through the support to red light, the sound track area being masked to prevent exposure at this stage. The film is then developed in a blue-green color forming developer such as that disclosed in Mannes,

' Godowsky and Wilder United States application 'Serial No. 185,700 to form blue-green positive image l8 in layer ll. Similarly, the top layer is exposed to blue light from the emulsion side and developed in a yellow color forming developer to form positive image IS in emulsion layer l3.

The sound track area also masked during the United States Patent 2,143,787, or: the edge of the film may be immersed in the sulfide and iodide bath so that the picture area of the film is not affected. After formation of the silver sulfide and silver iodide sound image 20, the middle layer picture area is fogged either by chemicals or by light and a magenta positive image is formed in this layer by meansof a suitable color forming developer such as that described in vMannes, Godowsky and Wilder United States application Serial No. 185,700. The film is then treated in suitable bleaching and hypo baths to used to form the sound track may be varied over wide limits to obtain any desired contrast as well as any highlight and maximum density. Although sulfide and thiourea are generally used for sulfiding, any substance which will react with silver halide to form silver sulfide may be substituted for, the sodium sulfide or thiourea. pH of the solution is controlled by the addition of alkali'such as sodium hydroxide to prevent 1 the formation of hydrogen sulfide gas.

The following general formula indicates a'suitable range of concentrations:

Potassium iodide grams.. To 800 Sodium sulfide 9H2O d0 'T0 400 15 Sodium hydroxide do To 800 Water to or- 1000 The following specific examples, which are illustrative only, indicate typical formulae which may be used:

Example 1' I Potassium iodide grams 200- Sodium hydroxide.. do 50 Thiourea 20 Water to m- 1000 Example 2 5 Potassium iodide grams 200 Sodium hydroxide do 50 Sodium' sulfide 9H2O d0 20 Water to cc 1000 Example 3 Sodium iodide grams-- 600 Sodium hydroxide do Sodium sulfide 911:0 do 400 Water to cc 1000 In some cases it has been found necessary to use a solution which is nearly saturated with potassium iodide and sodium sulfide in order to produce a sound track having uniform density throughout the sound track area. When the film is dipped intothe solution edgewise, the density of the sound track is sometimes less at 45 the top than at the bottom of the sound track area, unless concentrated solutions are used.

It is to be understood that my method is susceptible of numerous variations comingv within the scope of the appended claims.

1 claim:

. 1. The method of producing a sound track in a photographic film. which comprises printing .ithe sound track image on the film, developing the film to a negative sound image, and treating the sound track area of the film with a combineda photographic film, which comprises printing the sound track image on the film, developing .the film to a negative sound image, and treating the sound track area of the film with a combined sodium sulfide" and potassium iodide solution to form a combined silver sulfide and silver iodide sound track in the film.

3. The method of producing a combined sound track and picture image in a multi-layer photoremove all metallic silver and to leave the silver ph fi w c co p Printing e'sound sulfide and/or silver iodide sound image'iii the sound track area and the dye images 2|, 22 and 23 in layers ll, 12 and I3, respectively.

As indicated above, the range of iodide formingand sulfide forming compounds in the bath track and picture images on the film and developing them to a negative, successively exposing separate emulsion layers while masking the sound track area, and developing them in colorforming developers, treating the sound track The area in a combined sulilding and iodizing bath to form a. combined silver sulfide and silver iodide sound track, and removing from the him the metallic silver images formed in the several development steps.

4. The method of producing a combined sound track and picture image in a multi-layer photographic illm, which comprises printing the sound track and picture images on the film and developing them to a negative, successively exposing 10 LE ROY M. DEARING. 

